Probe continues for baby murder clues

Police will continue to investigate how the body of a baby girl washed ashore kilometres up the cost from northern NSW after wrapping up a waterways search for clues to the child's murder.

Detectives believe the nine-month-old girl was drowned in the area of the Jack Evans Harbour at Tweed Heads between 6pm and 7pm on Saturday, November 17.

The parents are believed to have caught a bus from the alleged murder site in NSW to Queensland in the hours following the death.

They were arrested at Broadbeach the following Monday just minutes before the baby's lifeless body was discovered by a passer-by five kilometres north.

The girl's 48-year-old father was later charged with her murder.

A week later, on Monday, police divers searched the bed of the Tweed River and the harbour foreshore for evidence.

They also examined water currents to establish if it was possible for the girl's body, in the middle of a storm, to be taken out to sea and carried more than 20 kilometres north.

Forensic, marine and other scientific experts are planning further tests with a baby-sized manikin to prove the macabre chain of events.

But now investigators are picking through hours of CCTV and witness statements from the communities of Kingscliff, Tweed Heads and Surfers Paradise to verify the family's movements in the lead up to the death.

The family, who can not be identified for legal reasons, was homeless and believed to be camping on beaches.

The mother remains in the care of mental health authorities and has not been charged, but police have refused to rule it out as the investigation progresses.